The present invention relates to composite structures and more particularly to composite structures of an organic matrix composite (OMC) type utilised to form components such as vanes and other elements within gas turbine engines.
Referring to FIG. 1, a gas turbine engine is generally indicated at 10 and comprises, in axial flow series, an air intake 11, a propulsive fan 12, an intermediate pressure compressor 13, a high pressure compressor 14, combustion equipment 15, a high pressure turbine 16, an intermediate pressure turbine 17, a low pressure turbine 18 and an exhaust nozzle 19.
The gas turbine engine 10 works in a conventional manner so that air entering the intake 11 is accelerated by the fan 12 which produce two air flows: a first air flow into the intermediate pressure compressor 13 and a second air flow which provides propulsive thrust. The intermediate pressure compressor compresses the air flow directed into it before delivering that air to the high pressure compressor 14 where further compression takes place.
The compressed air exhausted from the high pressure compressor 14 is directed into the combustion equipment 15 where it is mixed with fuel and the mixture combusted. The resultant hot combustion products then expand through, and thereby drive, the high, intermediate and low pressure turbines 16, 17 and 18 before being exhausted through the nozzle 19 to provide additional propulsive thrust. The high, intermediate and low pressure turbine 16, 17 and 18 respectively drive the high and intermediate pressure compressors 14 and 13, and the fan 12 by suitable interconnecting shafts.
In view of the above it will be appreciated that gas turbine engines operate at relatively high temperatures and provide stressing and loads which vary both cyclically as well as in terms of intensity during an operational cycle. Gas turbine engines utilised for aircraft propulsion have an ongoing objective of weight reduction. In such circumstances use of composite materials which allow a reduction in weight are advantageous.
Composite materials have been utilised in gas turbine engines and other situations previously. With regard to gas turbine engines achievement of acceptable safety criteria and component life, at least relative to traditional components to provide the same function, are clear requirements.
Composite structures generally comprise a laminar core which is assembled either as a single laminar core ply of materials appropriately shaped or more typically laminar core assemblies comprising a number of laminar cores appropriately arranged and conformed together to provide a conjunction as a joint within a component. To be acceptable a laminar core assembly, as indicated, should meet desired criteria and in particular thickness strength in such areas as vane fillets in the laminar core assembly. Nevertheless, these components may be subject to a range of loadings in particular impacts which must be considered.